sometimes key mapping wasn't working anymore,
turns out it's because using pacman to install packages, these would run: source /etc/profile
which restores the keymap
and so for Home key (on keypad) to work on vim again, I have to do: xmodmap ~/.Xmodmap

but here are the differences between the fixed way (aka normal) and the reverted to defaults (after source /etc/profile) way: see the *.diff files

